Long Period Fiber Gratings by Fiber-Tapering and Side-Coupling

• Main Authors: Pei-Jhen Jhuang, 莊佩蓁
• Other Authors: Yin-Chieh Lai
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/71605524365610764540

碩士 === 國立交通大學 === 光電工程系所 === 96 === In this thesis, we experimentally demonstrate a simple LPFG structure based on fiber-tapering and side-coupling techniques to form a flexible and high-sensitivity sensing device. The LPFG is composed of a fiber taper with a uniform waist of 20 μm in diameter and a side-contacted metal grating. The overlap of the evanescent field with the surface of metal grating leads to modal coupling along the propagation direction and provides an enhanced but opposite dip wavelength tuning tendency with respect to the temperature and refractive index change when compared to conventional LPFGs. The highest average refractive index tuning efficiency (dλ/dn) is 773 nm. The average temperature tuning efficiency is estimated to be about -0.24 nm/ °C, which is greatly improved when compared to that of conventional LPFGs (around +0.06 nm/ °C). The temperature and refractive index tuning characteristics of the LPFGs attributes to the unique material and waveguide dispersion characteristics of the proposed structure.